CHEVROLET TRUCK SENSOR PROBLEM

2000 Chevrolet Truck • 158,000 miles

I have a 2000 K2500 with 5.7L. Have been working on this issue for some time, when it first starts and I put it in drive, it runs like crap, bogs down, and chugs for the first minute. Doesn't matter if it has sit for hours or minutes, still does it. Replaced the fuel filter, checked the Oxygen sensors, plugs, wires, updated the computer and still does it. Only thing that works now is if I unplug the MAP sensor. Works great except for the check engine light.
Now, it is starting to do it again with the sensor unplugged. I had it at a mechanic and he couldn't figure it out either, even called some dealerships. I took it in and had the fuel pressure regulator changed too but that was a mistake, didn't change a thing.
Hoping whatever is going bad will finally just go and then it will be easier to figure out. Weird that it runs fine with the MAP sensor unplugged.
Any ideas would be appreciated!